The goals of the present research are to continue the investigations of the behavioral and neurochemical effects of repeated administration of methamphetamine. The effort is presently directed towards the determination of the mechanisms of the methamphetamine-induced depletion of dopamine in the caudate nucleus and its functional and behavioral effects. The observation that L-DOPA is capable of reversing methamphetamine-induced deficits in skilled motor performance is being studied in additional rhesus monkeys. Studies are also continuing which are attempting to determine the relationship between tolerance to the behavioral effects of methamphetamine and the depletion of caudate dopamine. Finally, several studies are continuing to exmaine the neurochemical mechanisms underlying the long-lasting caudate dopamine depletion induced by a four day dosing regimen of methamphetamine in rats.